Me pēnei te tohu i te whārangi:
Carl Walrond, 'Ngā whakaahua, ngā rauemi katoa', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/mi/rock-limestone-and-clay/media (accessed 12 December 2023)
He kōrero nā Carl Walrond, i tāngia i te 12 Jun 2006